1. Field of the Invention
The present invention relates to a gate valve which can open and close, and seal an aperture of a vacuum processing chamber. For example, the present invention relates to a gate valve which can open and close, and seal an aperture of a vacuum processing chamber to be used in a process of manufacturing a semiconductor device, etc.
2. Description of the Related Art
In dry-etching, sputtering and epitaxial wafer forming processes, etc. in manufacturing process of a semiconductor device, for example, there is used a vacuum processing device having a construction of a multi-chamber to which a plurality of vacuum processing chambers are connected as shown in FIG. 16.
In a vacuum processing device 301 in FIG. 16, a plurality of vacuum processing chambers 305 which conduct various kinds of processing are connected to an outer circumference of a conveying chamber 302 to which a wafer W is conveyed in and out. The movement between the conveying chamber 302 of the wafer W and each of vacuum processing chambers 305 is conducted through a gate G. The opening, closing and sealing of the gate G are conducted by a gate valve which is not shown in the drawings.
In the vacuum processing device 301 in FIG. 16, the wafer W is conveyed in the conveying chamber 302 by a conveying device which is not shown in the drawings through a conveying entrance 303 of a conveying channel 304, and is supported by a vacuum conveying robot 307 provided in the conveying chamber 302. When the wafer W is supported by the vacuum conveying robot 307, the conveying entrance 303 is closed, and a vacuum suction is conducted in the conveying chamber 302. At this time, each of said gate valves is in the state of sealing the respective gates. When the vacuum suction in the conveying chamber 302 is completed, each of the gate valves is actuated to open the gate G, and the wafer W is conveyed into a predetermined vacuum processing chamber by the vacuum conveying robot 307. For the processing in the vacuum processing chamber, each of the gate valves is actuated to close the gate G, and a predetermined processing is conducted on the wafer W. When the predetermined processing on the wafer W is completed, each of the gate valves is actuated to open the gate G, and the wafer W is carried out from the vacuum processing chamber by the vacuum conveying robot 307, and is automatically conveyed outside the vacuum processing device 301 through the conveying entrance 303.
As a gate valve 306 which can open and close, and seal the gate G in the above-mentioned vacuum processing device 301, the structures as shown in FIG. 17 and FIG. 18 are used.
In FIG. 17, a conveying chamber 202 is communicated with a vacuum processing chamber 203 through a gate G. The opening and closing of the gate G are conducted by a gate valve 201, and the gate valve 201 includes a valve plate 205 to conduct the opening and closing and sealing of the gate G, a valve rod 206 which has one end to which the valve plate 205 is fixed, and is supported to be capable of being moved straight and to be able to be inclined around a predetermined shaft 208, a seal bellows 207 which seals a space between the conveying chamber 202 and the valve rod 206, and an actuating means which is not shown in the drawings and moves straight or tilts the valve rod 206.
In FIG. 17, the gate valve 201 is in the state of opening the gate G. In order to close and seal the gate G, as shown in FIG. 18, the valve rod 206 is moved straight to be moved to the position where the valve plate 205 closes the gate G, and the valve rod 206 is tilted around a shaft 208. As a result, the valve plate 205 presses an O-ring 204 provided in the outer circumference of the gate G, so that the gate G is sealed.
However, in the gate valve 201 having the above-mentioned structure, for example, it is known that an air cylinder as a straight moving means and the valve rod 206 is connected through a cam mechanism, so that the tilting of the valve rod 206 is conducted.
For instance, a gate valve using such cam mechanism is disclosed in the official gazette of Japanese Patent No. 2613171.
The cam mechanism of the gate valve disclosed in the official gazette of Japanese Patent No. 2613171 is comprised of a pin which connects a yoke actuated straight by an air cylinder and a block fixed to a lower end portion of a valve rod, and a slanted elongate hole engaged with the pin.
In the cam mechanism having the construction, the pin slides with respect to the slanted elongate hole, and thus, a tilting force which tilts the valve rod is generated.
For instance, a gate valve using the cam mechanism is also disclosed in U.S. Pat. No. 5,120,019.
The cam mechanism disclosed in U.S. Pat. No. 5,120,019 is comprised of a cam plate including a cam surface which is moved straight by an air cylinder, and a cam follower comprised of a roller rotatably provided to a valve rod, and has the construction in which the roller is engaged with a cam surface of the straight moving cam plate so that the valve rod is tilted.
However, in the construction of the cam mechanism disclosed in the official gazette of Japanese Patent No. 2613171, because the pin slides over the inner circumferential surface of the slanted elongate hole, there is a disadvantage that a sliding friction is occurred therebetween and noise is easily generated, and thus, silence is insufficient.
Moreover, because the sliding friction is occurred between the pin and the inner circumferential surface of the slanted elongate hole, there is a disadvantage that the output of the air cylinder as an actuating means which actuates a cam mechanism needs to be raised, or it is difficult that the cam mechanism is smoothly operated, or the pin and the inner circumferential surface of the slanted elongate hole are easily worn, so that stable operation for long time period cannot be assured.
Further, in the cam mechanism of the construction disclosed in U.S. Pat. No. 5,120,019, because the roller as a cam follower rolls over the cam surface of the cam plate, it is difficult that the sliding friction is occurred, and generally, rolling friction is occurred. Accordingly, though the operation of the cam mechanism is comparatively smooth and the silence is excellent, because the roller needs to be rotatably supported by the supporting shaft, the structure becomes complicated, a bearing is needed between the roller and the supporting shaft, and there was a problem in the reliability of the bearing because a large radial load is applied to the bearing.
In addition, since there is a limitation to reduce a diameter of the roller, the structure was disadvantageous in view of compactness.
An object of the present invention is to provide a gate valve including a cam mechanism in which the structure thereof is simplified and small-sized so that low-price is possible.
A further object of the present invention is to provide a gate valve which has smooth operation so that high speed movement is possible, and has sufficient silence and high reliability.
Further, another object of the present invention is to provide a gate valve which can conduct securely the releasing operation from the sealing state of an aperture by a valve plate.
A gate valve of the present invention comprises: a valve plate which is provided in an air-tight chamber, and open and close an aperture of the air-tight chamber and seal the aperture by tilting with respect to said aperture; a valve rod which has one end to which said valve plate is fixed, and is supported to be movable in a predetermined straight movement direction for opening and closing the aperture and to be able to tilt around a predetermined tilting axis; a sealing means which seals a space between said valve rod and said air-tight chamber to be movable; a restriction means which restricts the straight movement in the direction to close said aperture of said valve plate at a closed position where the valve plate closes the aperture; a tilting cam mechanism which converts supplied straight moving force into tilting force, and tilts said valve rod of which the straight movement is restricted at said closed position around said tilting axis in the direction where said valve plate seals said aperture; a seal-releasing cam mechanism which is provided independently of said tilting cam mechanism, and tilts said valve rod around said tilting axis in the direction to release the sealing of said valve plate in the state of sealing said aperture according to the supply of the straight moving force in the direction to open said aperture; and an actuating means for supplying the straight moving force to said tilting cam mechanism and said seal-releasing cam mechanism.
Preferably, said tilting cam mechanism comprises: a rolling body; a rolling body supporting member which has a supporting surface supporting a rolling surface of said rolling body so that said rolling body can be rotated, and is actuated by said actuating means; a cam member for tilting which is disposed facing said rolling body supporting member, has a cam surface on which said rolling body rolls to tilt said valve rod, and is connected to said valve rod side; and a lubricant storing member including an opposing surface which faces a part of the rolling surface of the rolling body rotatably supported to said rolling body supporting member, and storing a lubricant in a gap formed between the rolling surface and the opposing surface.
Preferably, said seal-releasing cam mechanism comprises: a roller member; a supporting member rotatably supporting said roller member; and a cam member for releasing the seal including a cam surface on which said roller member rolls.
Said roller member and said supporting member are provided in said valve rod side, and said cam member for releasing the seal is provided in said actuating means side.
More preferably, said sealing means comprises: a seal bellows portion freely expanded and contracted which has one end fixed to said valve rod and the other end fixed to said air-tight chamber side; and a dust seal portion which said valve rod is inserted to and prevents a dust produced in the air-tight chamber from intruding into the seal bellows while allowing the tilting of said valve rod.
In the present invention, when the rolling body supporting member is moved straight by the actuating means in the direction where the valve plate closes the aperture, the valve rod is moved in the direction and the straight movement thereof is restricted at the closed position.
Further, when the rolling body supporting member is actuated, the rolling body rotatably supported on the supporting surface of the rolling body supporting member moves rolling over the cam surface of the cam member for tilting.
Consequently, the valve rod is tilted, and the aperture is sealed by the valve plate.
At this time, because the rolling body rotates with respect to the supporting surface of the rolling body supporting member, the sliding friction is generated between the rolling body and the supporting surface, and the rolling friction is generated between the rolling body and the cam surface of the cam member for tilting.
Meanwhile, because a lubricant is stored between the opposing surface of the lubricant storing member and a portion of the rolling surface of the rolling body, when the rolling body rolls over the cam surface, it rotates with respect to the opposing surface.
When the rolling body rotates with respect to the opposing surface, the lubricant is attached to the rolling surface so that the whole circumference of the rolling surface becomes covered with the lubricant.
Accordingly, the space between the rolling body and the cam surface of the cam member for tilting is lubricated, and the rolling friction therebetween is reduced.
Further, the lubricant attached to the rolling surface is supplied between the rolling body and the supporting surface of the rolling body supporting member, so that the space between the rolling surface and the supporting surface is lubricated, and sliding friction therebetween is reduced.
After the aperture is sealed by the valve plate, when the valve rod is actuated in the direction to open the aperture of the air-tight chamber in the sealed state, the seal-releasing cam mechanism is operated.
Specifically, the roller member rotatably supported to the supporting member rolls over the cam surface of the cam member for releasing the seal, so that the valve rod is compulsively tilted in the direction to release the sealing of the aperture.
Accordingly, even in case where the seal member provided between the valve plate and the aperture is adhered by the heat, etc. or in case where the pressure difference which affects to strongly press the valve plate toward the aperture exists between the air-tight chamber and the atmosphere, the sealed state of the aperture by the valve plate can be securely released.
Also, in the present invention, the sealing means is constructed by the seal bellows and the dust seal. For example, when the dust comprised of deposition compounds produced in the air-tight chamber or a part of destroyed product, etc. intrudes into the seal bellows and inserted to the expansion and contraction portion of the seal bellows, cracks are easily occurred in the seal bellows, and it cannot perform the sealing function in some occasions. In those occasions, the dust seal prevents the dust from intruding into the seal bellows so that such disadvantages can be suppressed.